Field of the Invention
The present invention relates to an inspecting apparatus capable of detecting a crack present in a test piece formed of a transparent material, and also to a laser processing apparatus capable of detecting a crack present in a workpiece formed of a transparent material.
Description of the Related Art
There is disclosed in Japanese Patent Laid-open No. 2012-195472 a laser processing method for forming a laser processed groove on a wafer formed of a transparent material such as lithium tantalate (LiTaO3) and lithium niobate (LiNbO3), the front side of the wafer being partitioned by a plurality of division lines to define a plurality of separate regions where a plurality of surface acoustic wave (SAW) devices are individually formed. In this laser processing method, a pulsed laser beam is applied to the front side of the wafer along each division line, wherein the pulse width of the pulsed laser beam is set to 200 ps or less and the repetition frequency of the pulsed laser beam is set to 50 kHz or less. According to this laser processing method, a laser processed groove can be formed on the front side of the wafer along each division line without generating a crack in the wafer. After forming the laser processed groove on the front side of the wafer along each division line, an external force is applied along each division line to thereby divide the wafer into the individual SAW devices.